U.S. patent number 9,695,792 [Application Number 14/808,819] was granted by the patent office on 2017-07-04 for system and method for operating an ignition system.
This patent grant is currently assigned to Ford Global Technologies, LLC. The grantee listed for this patent is Ford Global Technologies, LLC. Invention is credited to Michael Damian Czekala, Garlan J. Huberts, Qiuping Qu.
United States Patent |
9,695,792 |
Huberts , et al. |
July 4, 2017 |
System and method for operating an ignition system
Abstract
A system and method for mitigating the possibility of missing
ignition coil commands is presented. In one example, one or more
ignition coils may not be charged and/or discharged during a
cylinder cycle in response to the absence of a voltage pulse
forming at least a portion of an ignition coil command.
Inventors: |
Huberts; Garlan J. (Milford,
MI), Czekala; Michael Damian (Canton, MI), Qu;
Qiuping (Troy, MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Assignee: |
Ford Global Technologies, LLC
(Dearborn, MI)
|
Family
ID: |
57738435 |
Appl.
No.: |
14/808,819 |
Filed: |
July 24, 2015 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170022959 A1 |
Jan 26, 2017 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02P
11/02 (20130101); F02P 9/002 (20130101); F02P
3/0554 (20130101); F02P 3/05 (20130101); F02P
3/04 (20130101); F02P 9/007 (20130101); F02P
9/007 (20130101); F02P 3/04 (20130101); F02P
3/04 (20130101) |
Current International
Class: |
F02P
9/00 (20060101); F02P 3/05 (20060101) |
Field of
Search: |
;701/115 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Huynh; Hai
Assistant Examiner: Laguarda; Gonzalo
Attorney, Agent or Firm: Voutyras; Julia McCoy Russell
LLP
Claims
The invention claimed is:
1. A method for an engine, comprising: commanding two different
ignition coil charging current times via a single conductor and two
ignition coil commands for a cylinder cycle; and ignoring a
presence of at least one voltage pulse providing at least a portion
of the two ignition coil commands in response to a voltage pulse
missing from the two ignition coil commands.
2. The method of claim 1, where the two ignition coil commands are
comprised of at least three separate voltage pulses of two pulse
widths, and where ignoring includes not charging or discharging an
ignition coil.
3. The method of claim 2, where ignoring the presence of the at
least one voltage pulse includes not charging or discharging an
ignition coil in response to a present voltage pulse.
4. The method of claim 1, where a second ignition coil is not
charged in the cylinder cycle in response to an absence of a first
portion of a first command of the two ignition coil commands.
5. The method of claim 1, where a second ignition coil is not
discharged to provide a spark at a spark plug in the cylinder cycle
in response to an absence of a second command of the two ignition
coil commands.
6. The method of claim 1, where a second ignition coil is not
discharged to provide a spark at a spark plug in the cylinder cycle
in response to an absence of a second portion of a first command of
the two ignition coil commands.
7. The method of claim 1, where the two ignition coil commands are
a basis for providing spark at a single spark plug.
8. The method of claim 1, further comprising charging and
discharging a first ignition coil in response to a voltage pulse of
a second command of the two ignition coil commands.
9. A method for an engine, comprising: commanding two different
ignition coil charging current times via a single conductor and two
ignition coil commands, a first of the two ignition coil commands
adjusting charging of a second ignition coil, a second of the two
ignition coil commands adjusting charging of a first ignition coil;
adjusting charging of the second ignition coil responsive to an
absence of a first portion of the first of the two ignition coil
commands in a first manner; adjusting charging of the second
ignition coil responsive to an absence of a second portion of the
first of the two ignition coil commands in a second manner; and
adjusting charging of the first ignition coil responsive to an
absence of the second of the two ignition coil commands in a third
manner.
10. The method of claim 9, where the two ignition coil commands are
provided during a single cycle of a cylinder, and where the first
manner includes not charging the second ignition coil in a cylinder
cycle where the first portion of the first of the two ignition coil
commands is absent.
11. The method of claim 9, where the two ignition coil commands are
directed to the first ignition coil and the second ignition coil,
and where the second manner includes continuing to charge the
second ignition coil in a cylinder cycle where the second portion
of the first of the two ignition coil commands is absent.
12. The method of claim 9, where the two ignition coil commands
include a command to the first ignition coil comprising a single
voltage pulse, and where the third manner includes charging and
discharging the second ignition coil without providing a spark at a
spark plug in a cylinder cycle where the second of the two ignition
coil commands is absent.
13. The method of claim 12, where the two ignition coil commands
include a command to the second ignition coil comprising two
voltage pulses.
14. The method of claim 9, where a spark is not induced at a spark
plug coupled to the second ignition coil when adjusting charging of
the second ignition coil in the first and second manners.
Description
FIELD
The present description relates to a system and method for
delivering spark to a spark ignited engine. The system and method
may be particularly useful for engines that operate lean or with
dilute mixtures.
BACKGROUND AND SUMMARY
A spark plug of a spark ignited engine may be supplied energy from
two ignition coils. The two ignition coils may increase the spark
energy and spark duration so that an engine may be operated with a
lean air-fuel mixture or diluted (e.g., via exhaust gas
recirculation (EGR)) to improve engine fuel economy and/or
emissions. Each of the two ignition coils may be charged and
discharged individually so that charging of one coil overlaps with
charging of the other coil. Further, the second ignition coil may
be discharged while the first ignition coil is being discharged to
increase discharge current supplied to the spark plug.
One way to control each of the two ignition coils is to control
current supplied to the two ignition coils via two control signals
delivered via two conductors. However, the number of coil control
conductors may be doubled as compared to an engine having one
ignition coil per cylinder. Further, if the first control signal or
second control signal is degraded for a particular engine cycle,
the engine may misfire or begin combustion in a cylinder at an
undesirable time due to undesirable spark timing. Therefore, it may
be desirable to provide a way of operating two ignition coils
without doubling a number of control wires and reducing a
possibility of misfire if ignition coil signal degradation
occurs.
The inventors herein have recognized the above-mentioned
disadvantages and have developed a method for providing spark to an
engine, comprising: commanding two different ignition coil charging
current times via a single conductor and two ignition coil commands
for a cylinder cycle; and ignoring the presence of at least one
voltage pulse providing at least a portion of the two ignition coil
commands in response to a voltage pulse missing from the two
ignition coil commands.
By ignoring a pulse width of a first of two ignition coil commands,
it may be possible to mitigate the possibility of engine misfire
and undesirable combustion timing. For example, if a first portion
of a first ignition coil command is absent, ignition coil charging
may be inhibited or not started in response to the presence of a
second portion of the first ignition coil command so that the
ignition coil does not discharge during a subsequent cylinder cycle
at a time coil discharge is not desirable. Similar mitigating
actions may be taken if a second of the two ignition coil commands
is absent or if a first portion of the first of the two ignition
coil commands is absent.
The present description may provide several advantages. In
particular, the approach reduces the possibility of providing spark
to a cylinder at undesirable timing. Further, the approach,
depending on circumstances, may still initiate coil discharging at
a desirable time. Additionally, the approach may be performed in
the proximity of ignition coils so that there may be a higher
degree of confidence that the ignition coil commands are being
properly processed and interpreted.
The above advantages and other advantages, and features of the
present description will be readily apparent from the following
Detailed Description when taken alone or in connection with the
accompanying drawings.
It should be understood that the summary above is provided to
introduce in simplified form a selection of concepts that are
further described in the detailed description. It is not meant to
identify key or essential features of the claimed subject matter,
the scope of which is defined uniquely by the claims that follow
the detailed description. Furthermore, the claimed subject matter
is not limited to implementations that solve any disadvantages
noted above or in any part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages described herein will be more fully understood by
reading an example of an example, referred to herein as the
Detailed Description, when taken alone or with reference to the
drawings, where:
FIG. 1 is a schematic diagram of an engine;
FIG. 2 is a schematic diagram of an ignition system;
FIG. 3 is an example plot showing operation of the ignition system
of FIG. 2;
FIGS. 4-6 show plots of example ways to mitigate ignition system
degradation according to the method of FIG. 7; and
FIG. 7 shows a method for mitigating the possibility of undesirable
spark events for a dual coil ignition system.
DETAILED DESCRIPTION
The present description is related to operating an ignition system
of a spark ignited engine. In one non-limiting example, a control
signal comprising a plurality of voltage pulses during a cylinder
cycle is supplied to an ignition coil module via a single wire. The
ignition coil module may selectively not charge and discharge an
ignition coil in response to one or more missing voltage pulses.
FIG. 1 shows an example engine and ignition system. FIG. 2 shows a
detailed view of the ignition system shown in FIG. 1. An example
ignition system control sequence is shown in FIG. 3. The
possibility of improperly timed spark may be reduced as shown in
the sequences of FIGS. 4-6. A method for reducing the possibility
of improperly timed spark is shown in FIG. 7.
Referring to FIG. 1, internal combustion engine 10, comprising a
plurality of cylinders, one cylinder of which is shown in FIG. 1,
is controlled by electronic engine controller 12. Engine 10
includes combustion chamber 30 and cylinder walls 32 with piston 36
positioned therein and connected to crankshaft 40. Combustion
chamber 30 is shown communicating with intake manifold 44 and
exhaust manifold 48 via respective intake valve 52 and exhaust
valve 54. Each intake and exhaust valve may be operated by an
intake cam 51 and an exhaust cam 53. The position of adjustable
intake cam 51 may be determined by intake cam sensor 55. The
position of adjustable exhaust cam 53 may be determined by exhaust
cam sensor 57.
Fuel injector 66 is shown positioned to inject fuel directly into
cylinder 30, which is known to those skilled in the art as direct
injection. Alternatively, fuel may be injected to an intake port,
which is known to those skilled in the art as port injection. Fuel
injector 66 delivers liquid fuel in proportion to a pulse width of
a signal from controller 12. Fuel is delivered to fuel injector 66
by a fuel system (not shown) including a fuel tank, fuel pump, and
fuel rail (not shown). In addition, intake manifold 44 is shown
communicating with optional electronic throttle 62 which adjusts a
position of throttle plate 64 to control air flow from air intake
42 to intake manifold 44.
Distributorless ignition system 88 provides an ignition spark to
combustion chamber 30 via spark plug 92 in response to commands
from controller 12. Universal Exhaust Gas Oxygen (UEGO) sensor 126
is shown coupled to exhaust manifold 48 upstream of catalytic
converter 70. Alternatively, a two-state exhaust gas oxygen sensor
may be substituted for UEGO sensor 126.
Converter 70 can include multiple catalyst bricks, in one example.
In another example, multiple emission control devices, each with
multiple bricks, can be used. Converter 70 can be a three-way type
catalyst in one example.
Controller 12 is shown in FIG. 1 as a conventional microcomputer
including: microprocessor unit 102, input/output ports 104,
read-only memory 106, random access memory 108, keep alive memory
110, and a conventional data bus. Controller 12 is shown receiving
various signals from sensors coupled to engine 10, in addition to
those signals previously discussed, including: engine coolant
temperature (ECT) from temperature sensor 112 coupled to cooling
sleeve 114; a position sensor 134 coupled to an accelerator pedal
130 for sensing force applied by foot 132; a measurement of engine
manifold pressure (MAP) from pressure sensor 122 coupled to intake
manifold 44; an engine position sensor from a Hall effect sensor
118 sensing crankshaft 40 position; a measurement of air mass
entering the engine from sensor 120; and a measurement of throttle
position from sensor 58. Barometric pressure may also be sensed
(sensor not shown) for processing by controller 12. In one aspect
of the present description, engine position sensor 118 produces a
predetermined number of equally spaced pulses every revolution of
the crankshaft from which engine speed (RPM) can be determined.
In some examples, the engine may be coupled to an electric
motor/battery system in a hybrid vehicle. The hybrid vehicle may
have a parallel configuration, series configuration, or variation
or combinations thereof. Further, in some examples, other engine
configurations may be employed, for example the engine may be
turbocharged or supercharged.
During operation, each cylinder within engine 10 typically
undergoes a four stroke cycle: the cycle includes the intake
stroke, compression stroke, expansion stroke, and exhaust stroke.
During the intake stroke, generally, the exhaust valve 54 closes
and intake valve 52 opens. Air is introduced into combustion
chamber 30 via intake manifold 44, and piston 36 moves to the
bottom of the cylinder so as to increase the volume within
combustion chamber 30. The position at which piston 36 is near the
bottom of the cylinder and at the end of its stroke (e.g., when
combustion chamber 30 is at its largest volume) is typically
referred to by those of skill in the art as bottom dead center
(BDC). During the compression stroke, intake valve 52 and exhaust
valve 54 are closed. Piston 36 moves toward the cylinder head so as
to compress the air within combustion chamber 30. The point at
which piston 36 is at the end of its stroke and closest to the
cylinder head (e.g., when combustion chamber 30 is at its smallest
volume) is typically referred to by those of skill in the art as
top dead center (TDC). In a process hereinafter referred to as
injection, fuel is introduced into the combustion chamber. In a
process hereinafter referred to as ignition, the injected fuel is
ignited by known ignition means such as spark plug 92, resulting in
combustion. During the expansion stroke, the expanding gases push
piston 36 back to BDC. Crankshaft 40 converts piston movement into
a rotational torque of the rotary shaft. Finally, during the
exhaust stroke, the exhaust valve 54 opens to release the combusted
air-fuel mixture to exhaust manifold 48 and the piston returns to
TDC. Note that the above is shown merely as an example, and that
intake and exhaust valve opening and/or closing timings may vary,
such as to provide positive or negative valve overlap, late intake
valve closing, or various other examples.
Referring now to FIG. 2, is a schematic of an example ignition
system. In this example, controller 12 includes an ignition coil
pre-driver circuits 280, one for each ignition coil module 89 that
may be operated to supply electrical energy to a spark plug of a
single cylinder. The ignition coil pre-driver circuit 280 supplies
a control signal comprising voltage pulses to interpretive logic
225. Where the engine includes N cylinders, N ignition coil
pre-driver circuits provide control signals for ignition modules
89. In this example, four ignition coil modules 89 are supplied
control signals via four ignition coil pre-driver circuits 280. One
ignition coil module 89 is shown in detail. Interpretive logic 225
may be included in a programmable hardware logic array 211 or as
part of executable instructions stored in non-transitory memory of
a central processing unit 212. Interpretive logic 225 monitors the
timing and level of a signal provided by pre-driver circuit 280 as
described in FIGS. 4-7. In one non-limiting example, the timing of
the signal provided by pre-driver circuit 280 may be as described
in FIG. 3.
For example, interpretive logic 225 changes a state of a signal
supplied to ignition coil driver 202 in response to a voltage pulse
of a second ignition coil command of the ignition command signal.
Interpretive logic changes a state of a signal supplied to ignition
coil driver 204 in response to voltage pulses of a first ignition
coil command of the ignition command signal. Interpretive logic 225
may output individual signals to ignition coil drivers 202 and 204.
The signals supplied to ignition coil drivers 202 and 204 by
interpretive logic 225 are synchronous with cylinder strokes of the
cylinder being supplied spark via first ignition coil 206 and
second ignition coil 208. In one example, at least one spark is
provided during each cycle of the cylinder receiving spark from
first ignition coil 206 and/or second ignition coil 208. For
example, a spark may be supplied once a cylinder cycle during a
compression stoke of the cylinder receiving spark. Further, in one
example, first ignition coil 206 has a different inductance than
second ignition coil 208.
Ignition coil drivers 202 and 204 are included in ignition system
ignition coil module 89 which may be positioned on top of or near
spark plug 92. Electric energy storage device 220 sources
electrical current to first ignition coil 206. Second ignition coil
208 is selectively supplied current via second coil driver 204.
Electric energy storage device 220 sources electrical current to
second ignition coil 208.
Spark plug 92 may be supplied electrical energy from first ignition
coil 206 and/or second ignition coil 208. Spark plug 92 includes a
first electrode 260 and a second electrode 262. Second electrode
262 may be in continuous electrical communication with ground 240.
A spark may develop across gap 250 when an electrical potential
difference exists between first electrode 260 and second electrode
262.
Thus, the system of FIGS. 1 and 2 provides for a system for
supplying spark to an engine, comprising: a ignition coil
pre-driver circuit; interpretive logic that is in electrical
communication with the first ignition coil pre-driver circuit, the
interpretive logic including two ignition coil driver outputs, the
interpretive logic including logic to ignore the presence of at
least one voltage pulse providing at least a portion of two
ignition coil commands from the ignition coil pre-driver circuit in
response to a voltage pulse missing from the two ignition coil
commands. The system includes where the interpretive logic is
hardware logic. The system includes where the interpretive logic
includes executable instructions stored in non-transitory
controller memory. The system includes where the interpretive logic
is in electrical communication with two ignition coil drivers. The
system includes where the two ignition coil drivers are in
electrical communication with two ignition coils. The system
includes where the two ignition coils are in electrical
communication with a sole spark plug.
Referring now to FIG. 3, a plot showing control signals for an
ignition system that includes two ignition coils (e.g., the system
of FIG. 2) via receiving commands for the two ignition coils via a
single conductor during a single cylinder cycle. The signals
represent signals that control the two coils (e.g., 206 and 208 of
FIG. 2) that provide spark to a single cylinder (e.g., cylinder
number one). The signals shown are for one cylinder cycle where
ignition system degradation is not present. Signals for other
engine cylinders similar to those shown are also provided. Vertical
markers T0-T6 represent times of particular interest during the
sequence.
The first plot from the top of FIG. 3 shows an ignition coil
command signal provided via a single conductor that is the basis
for operating the first and second ignition coils supplying
electrical energy to a single spark plug. The ignition coil command
signal timing changes in response to engine speed, engine load,
engine combustion mode (e.g., lean or dilute) among other
variables.
The second plot from the top of FIG. 3 shows a first ignition coil
charging current. The charging current flows into a primary coil in
the first ignition coil. A dwell time is an amount of time that
charging current flows into the ignition coil. Electrical energy is
being stored in the first ignition coil of two ignition coils
supplying energy to a spark plug when charging current flows into
the first ignition coil. The amount of energy stored in the first
ignition coil increases as the charging current moves in the
direction of the vertical axis arrow. The first ignition coil is
not charging when the first charging current is at a lower level
near the horizontal axis.
The third plot from the top of FIG. 3 shows a second ignition coil
charging current. The second ignition coil of the two ignition
coils supplying energy to the lone spark plug is charging when the
second coil charging current is increasing. The second ignition
coil is increasing when the second ignition coil charging current
signal is increasing in the direction of the vertical axis arrow.
The second ignition coil is not charging when the second ignition
coil charging current signal is at a lower level near the
horizontal axis.
The fourth plot from the top of FIG. 3 represents potential
operating states for the first and second ignition coils. The
operating states correspond to operation of the first and second
ignition coils according to the state table 320. For example, in
state number two, only the second ignition coil is being charged.
In state number three, both the first and second ignition coils are
being charged.
At time T0, both ignition coils are not being charged and the
command signal is at a lower level. The operating state is zero
indicating the ignition coils are not charging or commanded to
charge.
Between time T0 and time T1, a first voltage pulse 302 during a
cylinder cycle is provided. The first voltage pulse is a short
duration pulse (e.g., less than 75 microseconds), and it indicates
a beginning of charging of a second ignition coil for the cylinder
cycle. Because the first pulse 302 is less than 75 microseconds, it
may be interpreted solely as a command for the second ignition coil
(e.g., ignition coil 208 of FIG. 1). Further, it is a first portion
of a command for operating the second ignition coil because it
provides a starting time or engine position for charging the second
ignition coil, but it does not provide a stopping time or engine
position for discharging the second ignition coil. The second
ignition coil begins to charge after falling edge 302B transitions
to a low level. The ignition coil state is a value of zero to
indicate ignition coil 1 and ignition coil 2 are not activated.
Shortly before time T1, the first voltage pulse 302 ends by
transitioning to a low level.
At time T1, the second ignition coil (e.g., 208 of FIG. 2) begins
to charge by providing battery power to the second ignition coil
via ignition coil driver 204 in response to first voltage pulse
302. In particular, the charging current of the second ignition
coil begins to increase. The first coil is not charging because the
first coil charging coil is zero. The potential coil states are
zero and two. If the first voltage pulse 302 was missing, the coil
state would be zero. However, since the first voltage pulse 302 is
present, the coil state is two.
Between time T1 and time T2, the second voltage pulse 304 occurs.
The second voltage pulse 304 is a long duration pulse (e.g.,
greater than 105 microseconds). Because the second pulse 304 is
greater than 75 microseconds, it may be interpreted solely as a
command for the first ignition coil (e.g., ignition coil 206 of
FIG. 1). The rising edge 304A identifies start of charging for
ignition the first ignition coil. The falling edge 304B identifies
stop of charging or discharge time for the first ignition coil. The
potential coil states are one and three.
At time T2, the first ignition coil begins to charge in response to
the second voltage pulse 304. The first ignition coil may begin to
charge after the 105 micro-second time duration has been exceeded
via the second voltage pulse 304. Thus, in this example, the first
ignition coil and the second ignition coil are charging at time T2.
If the first voltage pulse 302 was not present and second voltage
pulse 304 was present for the cylinder cycle, the coil state would
be one. The coil state is three when the first pulse 302 and the
second pulse 304 are present.
Between time T2 and time T3, the second voltage pulse 304 ends. The
second voltage pulse ends at falling edge 304B. The second ignition
coil continues to charge.
At time T3, a spark is initiated at the spark plug in response to
the second voltage pulse ending. The ending time of second voltage
pulse 304 corresponds to a desired spark timing crankshaft angle
(e.g., 15 degrees advanced of top dead center for the cylinder
receiving the spark). The second ignition coil continues to charge
after the first ignition coil begins to discharge.
Between time T3 and time T4, a third voltage pulse 306 for the
cylinder cycle occurs. The third voltage pulse 306 is a short
duration pulse (e.g., less than 75 microseconds). The third voltage
pulse 306 indicates an ending time for charging the second ignition
coil. Thus, the third voltage pulse 306 is a second portion of a
command for operating the second ignition coil. Alternatively,
first voltage pulse 302 may be interpreted as a first command to
operate the second ignition coil for the cylinder cycle, and third
voltage pulse 306 may be interpreted as a second command to operate
the second ignition coil for the cylinder cycle. If the first
voltage pulse 302 was not present, the coil state would be zero.
The coil state is two when the first pulse 302 is present.
At time T4, the second ignition coil is discharged in response to
the third voltage pulse 306. Thus, both the first and second
ignition coils are discharged before time T4. The first and second
ignition coils are discharged during a same cylinder cycle and the
commands to charge and discharge the respective first and second
ignition coils also occur during the same cylinder cycle.
Between time T4 and time T5, both the first and second ignition
coils are discharging. Voltage pulse 308 is a long duration pulse
(e.g., 105 microseconds). Therefore, it is determined to be a
command for the first ignition coil (e.g., 206 of FIG. 1). This
starts the recharging of the first ignition coil for restriking of
the spark plug during the same cylinder cycle. Since the first
ignition coil is typically a low inductance coil, it can be
recharged quickly and recharging and restriking may occur
repeatedly during the same cylinder cycle at lower engine speeds
(e.g., less than 2000 RPM).
At time T5, the first ignition coil begins to recharge. The second
ignition coil is not charging and the ignition state is one.
However, if pulse 308 had not been sent, the ignition state would
have been zero since short duration voltages have not been sent for
the second ignition coil.
Between time T5 and time T6, the first voltage pulse for the second
cylinder ends by transitioning to a lower level. The falling edge
308B is at a time that represents a desired angle of spark
augmentation. The second ignition coil is not charged for the
entire duration of the restrike period.
At time T6, the first ignition coil is discharged for restrike
spark augmentation. The cylinder cycle ends after time T6 and a new
cylinder cycle begins. The ignition state is zero since the first
and second ignition coils are discharged.
In this way, two ignition coils may be selectively charged and
discharged to during a cylinder cycle to vary an amount of
electrical energy supplied to a spark plug during a cylinder cycle.
Control commands for the two ignition coils may be provided over a
single conductor to reduce wiring and system complexity.
Referring now to FIG. 4, an example plot showing a way to mitigate
ignition system degradation is shown. In particular, FIG. 4 shows
example signals during conditions when a second short duration
voltage pulse during a cylinder cycle (e.g., the third voltage
pulse in the cylinder cycle) is not present or is missing. The
sequence of FIG. 4 may be provided by the method of FIG. 7 as part
of the system of FIGS. 1 and 2. Vertical lines from time T10-T18
represent times of interest in the sequence. A first cylinder cycle
begins at a time before T10 and ends before time T16. A second
cylinder cycle begins at the end of the first cylinder cycle before
time T16.
The first plot from the top of FIG. 4 shows an ignition coil
command signal provided via a single conductor that is the basis
for operating the first and second ignition coils supplying
electrical energy to a single spark plug. The ignition coil command
signal timing changes in response to engine speed, engine load,
engine combustion mode (e.g., lean or dilute) among other
variables. Short duration voltage pulses (e.g., a predetermined
time such as less than 75 microseconds) as shown at 402 and 406
provide first (charge second ignition coil) and second instructions
(discharge second ignition coil) for operating a second ignition
coil. The dwell time for the second ignition coil is the time
between the falling edge of the first voltage pulse of pulse 402
and the falling edge of second voltage pulse 406. Long duration
voltage pulse with (e.g., a predetermined time longer than 105
microseconds) as shown at 404 provides the start charging time,
discharge time, and dwell time for charging the first ignition
coil. The start charging time for the first ignition coil is based
on the rising edge of pulse 404. The discharge time for the first
ignition coil is based on the falling edge of pulse 404. The dwell
time for the first ignition coil is the time between the rising and
falling edges of pulse 404. The discharge time corresponds to an
engine crankshaft position for desired spark (e.g., 20 degrees
BTDC).
The second plot from the top of FIG. 4 shows a second ignition coil
charging current. The second ignition coil of the two ignition
coils supplying energy to the lone spark plug is charging. The
second ignition coil is increasing when the second ignition coil
charging current signal is increasing in the direction of the
vertical axis arrow. The second ignition coil is not charging when
the second ignition coil charging current signal is at a lower
level near the horizontal axis.
The following times are typical times for when the engine is
operating at a speed of 6000 RPM. A time between time T10 and time
T13 is 5 milliseconds. A time between time T12 and time T13 is 2
milliseconds. A time between time T11 and time T12 is 2
milliseconds. A time between time T10 and time T11 is 3
milliseconds. A time between time T10 and time T16 is 20
milliseconds. A time between time T12 and time T14 is 5
milliseconds. The duration of ignore window 410 is 5
milliseconds.
FIG. 4 shows an example sequence for mitigating the possibility of
undesirable spark timing when a second of two voltage pulses
commanding a second ignition coil (e.g., a discharge command for a
second ignition coil) is missing or not detected during a cylinder
cycle. During nominal operating conditions, three voltage pulses
occur during each cycle of each cylinder. During the cylinder
cycle, a second ignition coil begins charging in response to a
falling edge of a first voltage pulse 402 (e.g., short duration
less than 75 micro seconds) and discharges in response to a falling
edge of a third voltage pulse 406 (e.g., short duration less than
75 micro seconds). A first ignition coil begins charging in
response to a rising edge of second voltage pulse 404 (e.g., short
duration less than 75 micro seconds), and the first ignition coil
discharges in response to the falling edge of voltage pulse 404.
However, in this example, the third voltage pulse or second portion
of a command to operate the second ignition coil is missing as
indicated by the dotted lines.
At time T10, the falling edge of a first voltage pulse representing
a first portion of a command to operate the second ignition coil is
received by interpretive logic 225 of FIG. 2. The interpretive
logic initiates charging of the second ignition coil as indicated
by the second charging coil current increasing. The first ignition
coil is not charged and does not begin charging at time T10.
At time T11, the interpretive logic identifies the rising edge of
the second voltage pulse 404 after it is at a high level for longer
than 105 microseconds. The interpretive logic begins charging the
first ignition coil (not shown). The second ignition coil continues
charging.
At time T12, the interpretive logic identifies the falling edge of
the second voltage pulse 404 and discharges the first ignition coil
(not shown). The second ignition coil continues charging.
At time T13, the third voltage pulse (short duration) goes missing
or undetected as indicated by the dotted lines. Because the third
voltage pulse is undetected during the cylinder cycle, the second
ignition coil continues to charge for a predetermined amount of
time which ends at time T14. When the predetermined amount of time
expires without detecting the third voltage pulse, commands for the
second coil (e.g., voltage pulses less than 75 microseconds) are
not excepted, processed, or responded to for a predetermined amount
of time (e.g., 5 milliseconds) as indicated by the ignore window
410. Further, current supplied to the second ignition coil is
ramped down at a predetermined rate that is much slower than an
amount of time it takes to disrupt current flow into the second
ignition coil when the second ignition coil is discharged in
response to a falling edge of a third voltage pulse during a
cylinder cycle. Consequently, discharging the second ignition coil
at a slow rate does not induce a spark at the spark plug.
Therefore, the second ignition coil is not discharged to induce a
spark at the spark plug at a time later than spark is desired to be
supplied during the cylinder cycle. In this way, a spark at an
undesirable time may be avoided. The second ignition coil is
discharged before time T16.
At time T16, a first voltage pulse (e.g., short duration of less
than 75 micro seconds) for the second ignition coil during a second
cylinder cycle (e.g., four strokes) is received by the interpretive
logic. The second ignition coil begins charging shortly after the
falling edge observed at time T16.
Between time T16 and time T17, a first ignition coil is charged and
discharged in response to a second voltage pulse (e.g., a long
duration voltage pulse greater than 105 microseconds) for the
second ignition coil during the second engine cycle. The second
ignition coil continues to charge.
At time T17, a second voltage pulse (e.g., short duration of less
than 75 micro seconds) for the second ignition coil during a second
engine cycle is received by the interpretive logic. The second
ignition coil is discharged shortly after the falling edge of the
second short duration voltage pulse is received during the second
cylinder cycle. Discharging the second ignition coil increases
electrical energy delivered to the spark plug during the cylinder
cycle. Thus, spark timing resumes in an expected way after the both
short duration voltage pulses are detected during the second
cylinder cycle.
Commands for the second ignition coil (e.g., short duration pulse
widths) are not responded to or no action is performed in response
to short duration voltage pulses of the command signal in the
second ignore window between time T17 and time T18. The ignore
window has a duration of a predetermined amount of time.
In this way, mistiming of spark from a second ignition coil to a
spark plug while a first ignition coil is discharging to the spark
plug may be avoided. This may be particularly useful to avoid
providing untimely spark during a subsequent cylinder cycle since
delayed spark discharge may lead to providing spark during a
subsequent cylinder cycle. Further, the ignore window 410 provides
time for the second ignition coil to discharge to a low level where
spark may not be provided at the spark plug via the second ignition
coil at times after the ignore window and before subsequent second
ignition coil commands are received in a subsequent cylinder
cycle.
Referring now to FIG. 5, an example plot showing a way to mitigate
ignition system degradation is shown. In particular, FIG. 5 shows
example signals during conditions when a first short duration
voltage pulse during a cylinder cycle (e.g., first voltage pulse
during the cylinder cycle) is not present or is missing. The
sequence of FIG. 5 may be provided by the method of FIG. 7 as part
of the system of FIGS. 1 and 2. Vertical lines from time T20-T27
represent times of interest in the sequence. A first cylinder cycle
begins at a time before T20 and ends before time T25. A second
cylinder cycle begins at the end of the first cylinder cycle before
time T25.
The first plot from the top of FIG. 5 shows an ignition coil
command signal provided via a single conductor that is the basis
for operating the first and second ignition coils supplying
electrical energy to a single spark plug. The ignition coil command
signal timing changes in response to engine speed, engine load,
engine combustion mode (e.g., lean or dilute) among other
variables. Short duration voltage pulses (e.g., a predetermined
time such as less than 75 microseconds) as shown at 502 and 506
provide first (charge second ignition coil) and second instructions
(discharge second ignition coil) for operating a second ignition
coil. The dwell time for the second ignition coil is the time
between the falling edge of the first voltage pulse of pulse 502
and the falling edge of second voltage pulse 506. Long duration
voltage pulse with (e.g., a predetermined time longer than 105
microseconds) as shown at 504 provides the start charging time,
discharge time, and dwell time for charging the first ignition
coil. The start charging time for the first ignition coil is based
on the rising edge of pulse 504. The discharge time for the first
ignition coil is based on the falling edge of pulse 504. The dwell
time for the first ignition coil is the time between the rising and
falling edges of pulse 504. The discharge time corresponds to an
engine crankshaft position for desired spark (e.g., 20 degrees
BTDC).
The second plot from the top of FIG. 5 shows a second ignition coil
charging current. The second ignition coil of the two ignition
coils supplying energy to the lone spark plug is charging. The
second ignition coil is increasing when the second ignition coil
charging current signal is increasing in the direction of the
vertical axis arrow. The second ignition coil is not charging when
the second ignition coil charging current signal is at a lower
level near the horizontal axis.
The following times are typical times for when the engine is
operating at a speed of 6000 RPM. A time between time T20 and time
T23 is 5 milliseconds. A time between time T22 and time T23 is 2
milliseconds. A time between time T21 and time T22 is 2
milliseconds. A time between time T20 and time T21 is 3
milliseconds. A time between time T20 and time T25 is 20
milliseconds. The duration of ignore window 510 is 10
milliseconds.
FIG. 5 shows an example sequence for mitigating the possibility of
undesirable spark timing when a first of two voltage pulses
commanding a second ignition coil (e.g., a charging command for the
second ignition coil) is missing or not detected during a cylinder
cycle. During nominal operating conditions, three voltage pulses
occur during each cycle of each cylinder. During the cylinder
cycle, a second ignition coil begins charging in response to a
falling edge of a first voltage pulse 502 (e.g., short duration
less than 75 micro seconds) and discharges in response to a falling
edge of a third voltage pulse 506 (e.g., short duration less than
75 micro seconds). A first ignition coil begins charging in
response to a rising edge of second voltage pulse 504 (e.g., short
duration less than 75 micro seconds), and the first ignition coil
discharges in response to the falling edge of voltage pulse 504.
However, in this example, the first voltage pulse or first portion
of a command to operate the second ignition coil is missing as
indicated by the dotted lines.
At time T20, the falling edge of a first voltage pulse representing
a first portion of a command to operate the second ignition coil is
not received by interpretive logic 225 of FIG. 2. The location of
the missing voltage pulse is indicated by the dotted lines at 502.
The interpretive logic does not initiate charging of the second
ignition coil as indicated by the second charging coil current not
increasing. The first ignition coil is not charged and does not
begin charging at time T20.
At time T21, the interpretive logic identifies the rising edge of
the second voltage pulse 504 after it is at a high level for longer
than 105 microseconds. The interpretive logic begins charging the
first ignition coil (not shown). The second ignition coil does not
charge.
At time T22, the interpretive logic identifies the falling edge of
the second voltage pulse 504 and discharges the first ignition coil
(not shown). The second ignition coil does not charge. In addition,
an ignore window opens so that any short duration pulses are not
acted upon (no coil charging or discharging) for a predetermined
amount of time (e.g., 10 milliseconds). The duration of the ignore
window is increased as compared to the condition where the third
voltage pulse during the cylinder cycle goes missing so that
charging of the ignition coil is delayed until a following cylinder
cycle (e.g., a second cylinder cycle). By not responding to voltage
pulses that are second ignition coil commands, mistimed spark
events may be avoided.
At time T23, the third voltage pulse (short duration) is ignored so
that the second ignition coil does not begin charging late in the
first cylinder cycle. The charging of the second ignition coil may
resume its regular procedure during the following or second
cylinder cycle. This allows the second ignition coil to be charged
to a desired level and to be discharged at a desired crankshaft
angle.
At time T24, the ignore window closes and short duration voltage
pulses may once again be interpreted as commands for the charging
and discharging of the second ignition coil. The first and second
ignition coils are not storing charge at time T24 and no ignition
coil commands are present.
At time T25, a first voltage pulse (e.g., short duration of less
than 75 micro seconds) for the second ignition coil during a second
cylinder cycle (e.g., four strokes) is received by the interpretive
logic. The second ignition coil begins charging shortly after the
falling edge observed at time T25.
Between time T25 and time T26, a first ignition coil is also
charged and discharged in response to a second voltage pulse (e.g.,
a long duration voltage pulse greater than 105 microseconds) for
the second ignition coil during the second engine cycle. The second
ignition coil continues to charge.
At time T26, a falling edge of a second voltage pulse (e.g., short
duration of less than 75 micro seconds) for the second ignition
coil during a second engine cycle is received by the interpretive
logic. The second ignition coil is discharged shortly after the
falling edge of the second short duration voltage pulse is received
during the second cylinder cycle. Discharging the second ignition
coil increases electrical energy delivered to the spark plug during
the cylinder cycle. Thus, spark timing resumes in an expected way
after the both short duration voltage pulses are detected during
the second cylinder cycle.
In this way, mistiming of spark from a second ignition coil to a
spark plug while a first ignition coil is discharging to the spark
plug may be avoided. This may be particularly useful to avoid
providing untimely spark during a subsequent cylinder cycle since
the second ignition coil is not charged until a subsequent cylinder
cycle. Further, the ignore window 510 inhibits the second ignition
coil from charging so that a desired dwell time and amount of spark
energy may be provided during the subsequent cylinder cycle.
Referring now to FIG. 6, an example plot showing a way to mitigate
ignition system degradation is shown. Specifically, FIG. 6 shows
example signals during conditions when a long duration voltage
pulse (e.g., a first coil command) during a cylinder cycle is not
present or missing. The sequence of FIG. 6 may be provided by the
method of FIG. 7 as part of the system of FIGS. 1 and 2. Vertical
lines from time T30-T37 represent times of interest in the
sequence. A first cylinder cycle begins at a time before T30 and
ends before time T34. A second cylinder cycle begins at the end of
the first cylinder cycle before time T34.
The first plot from the top of FIG. 6 shows an ignition coil
command signal provided via a single conductor that is the basis
for operating the first and second ignition coils supplying
electrical energy to a single spark plug. The ignition coil command
signal timing changes in response to engine speed, engine load,
engine combustion mode (e.g., lean or dilute) among other
variables. Short duration voltage pulses (e.g., a predetermined
time such as less than 75 microseconds) as shown at 602 and 606
provide first (charge second ignition coil) and second instructions
(discharge second ignition coil) for operating a second ignition
coil. The dwell time is the time between the falling edge of the
first voltage pulse of pulse 602 and the falling edge of second
voltage pulse 606. Long duration voltage pulse with (e.g., a
predetermined time longer than 105 microseconds) as shown at 604
provides the start charging time, discharge time, and dwell time
for charging the first ignition coil. The start charging time is
based on the rising edge of pulse 604. The discharge time is based
on the falling edge of pulse 604. The dwell time is the time
between the rising and falling edges of pulse 604. The discharge
time corresponds to an engine crankshaft position for desired spark
(e.g., 20 degrees BTDC).
The second plot from the top of FIG. 6 shows a second ignition coil
charging current. The second ignition coil of the two ignition
coils supplying energy to the lone spark plug is charging. The
second ignition coil is increasing when the second ignition coil
charging current signal is increasing in the direction of the
vertical axis arrow. The second ignition coil is not charging when
the second ignition coil charging current signal is at a lower
level near the horizontal axis.
The following times are typical times for when the engine is
operating at a speed of 6000 RPM. A time between time T30 and time
T33 is 5 milliseconds. A time between time T32 and time T33 is 2
milliseconds. A time between time T31 and time T32 is 2
milliseconds. A time between time T30 and time T31 is 3
milliseconds. A time between time T30 and time T34 is 20
milliseconds. The duration of ignore window 610 is 10 milliseconds
beyond a falling edge of a second (long) voltage pulse during a
next cylinder cycle.
FIG. 6 shows an example sequence for mitigating the possibility of
undesirable spark timing when a second voltage pulse of a cylinder
that represents a command for a first ignition coil is missing or
not detected during a cylinder cycle. During nominal operating
conditions, three voltage pulses occur during each cycle of each
cylinder. During the cylinder cycle, a second ignition coil begins
charging in response to a falling edge of a first voltage pulse 602
(e.g., short duration less than 75 micro seconds) and discharges in
response to a falling edge of a third voltage pulse 606 (e.g.,
short duration less than 75 micro seconds). A first ignition coil
begins charging in response to a rising edge of second voltage
pulse 604 (e.g., long duration greater than 105 micro seconds), and
the first ignition coil discharges in response to the falling edge
of voltage pulse 604. However, in this example, the second voltage
pulse or the command to operate the first ignition coil is missing
as indicated by the dotted lines.
At time T30, the falling edge of a first voltage pulse representing
a first portion of a command to operate the second ignition coil is
received by interpretive logic 225 of FIG. 2. The interpretive
logic initiates charging of the second ignition coil as indicated
by the second charging coil current increasing. The first ignition
coil is not charged and does not begin charging at time T30.
At time T31, the interpretive logic fails to identify the rising
edge of the second voltage pulse 604 since it is missing. The
interpretive logic allows the second ignition coil to continue
charging. The first ignition coil is not storing charge and is not
being charged.
At time T32, the interpretive logic fails to identify the falling
edge of the second voltage pulse 604 and so the first ignition coil
is not discharged. Further, charging of the second ignition coil
continues.
At time T33, the third voltage pulse in a regular cylinder cycle is
detected, but the second ignition coil is not discharged because
the second coil discharge time would be late. Consequently, the
content of the cylinder in which the second voltage pulse is
missing is expelled without being combusted. Further, current
supplied to the second ignition coil is gradually ramped down to
reduce the charge stored in the second ignition coil. An ignore
window is also open and while the ignore window is open, the
interpretive logic does not respond to short duration or second
ignition coil commands. By not responding to second ignition coil
commands, it may be possible to reduce the possibility of losing
synchronization between the command signal and engine crankshaft
position. Therefore, spark events may occur at desired timings or
not at all during a cylinder cycle.
Between time T33 and time T34, a second ignition coil is slowly
discharged so as to not induce a spark at a spark plug that is in
electrical communication with the second ignition coil. The charge
in the second ignition coil is reduced so that a desired amount of
charge is stored in the second ignition coil when the second
ignition coil is subsequently charged.
At time T34, a first voltage pulse (e.g., short duration) for the
second ignition coil during a second cylinder cycle is received by
the interpretive logic. Nevertheless, because the ignore window 620
is open, the interpretive logic does not begin charging the second
ignition coil.
Between time T34 and time T35 the second voltage pulse (e.g., the
long duration pulse) is received and detected by the interpretive
logic. The interpretive logic may begin charging of the first
ignition coil in response to a rising edge of the second voltage
pulse. Alternatively, the interpretive logic may delay charging
both the first and second ignition coils until a predetermined
amount of time (e.g., 10 milliseconds) after a falling edge of the
second voltage pulse is detected. In this way, the interpretive
logic may inhibit spark production in a cylinder until all three
voltage pulse commands are detected in a cylinder cycle to reduce
the possibility of mistimed spark. Thus, early or late combustion
of the cylinder contents may be avoided.
At time T35, a falling edge of the second voltage pulse is detected
by the interpretive logic. The falling edge is the basis for
closing the ignore window so that short duration voltage pulses or
second coil commands may be interpreted and used to charge and
discharge the second ignition coil. The ignore window is closed a
predetermined amount of time (e.g., 10 milliseconds) after the
falling edge of the second voltage pulse is detected.
At time T36, a second voltage pulse (e.g., short duration of less
than 75 micro seconds, the third voltage pulse in the cylinder
cycle) for the second ignition coil during a second engine cycle is
received by the interpretive logic. However, the second ignition
coil is not discharged or charge in response to the voltage pulse.
Rather, the interpretive logic does not respond to the voltage
pulse. In this way, undesired charging of the second ignition coil
may be avoided.
At time T37, the ignore window closes so that first, second, and
third voltage pulses may be acted upon during a cylinder cycle.
This allows the first and second ignition coils to charge and
discharge, thereby resuming normal operation.
In this way, mistiming of spark from a second ignition coil to a
spark plug may be avoided when first ignition coil commands are not
present or detected. As a result, it may be possible to avoid
untimely spark events during a subsequent cylinder cycles.
Referring now to FIG. 7, a method for mitigating the possibility of
undesirable spark events for a dual coil ignition system is shown.
The ignition system may be similar to the ignition system shown in
FIG. 2. Additionally, at least portions of the method of FIG. 7 may
be included as executable instructions in the system of FIG. 1.
Further, at least portions of the method of FIG. 7 may be actions
taken within the ignition coil in the physical world to transform
ignition operation. The method of FIG. 7 may be applied to ignition
coils of all engine cylinders. The first ignition coil may be 206
of FIG. 2 and the second ignition coil may be 208 of FIG. 2. The
description of first, second, and third pulse widths used in the
method of FIG. 7 apply to pulse widths that are present if the
ignition system is operating without degradation even though for
specific conditions one of the first, second, or third pulse widths
may be missing.
At 702, method 700 begins to monitor an ignition coil command
signal for a cylinder cycle. The ignition coil command signal may
include voltage pulses that are the basis for operating two
ignition coils that provide electrical energy to a single spark
plug. In one example, the command signal may be of the form
described in FIGS. 3-6. Method 700 monitors the command signal for
short (e.g., less than 75 microseconds) and long duration voltage
pulses (e.g., greater than 105 microseconds). Further, method 700
detects rising and falling edges of voltage pulses. The command
signal is synchronized with engine crankshaft position so that the
voltage pulse edges indicate desired crankshaft positions for
discharging spark during a cylinder cycle. Method 700 proceeds to
704 after beginning to monitor the command signal.
At 704, method 700 judges if a first voltage pulse (e.g., short
duration pulse width) of an ignition coil command sequence for a
cylinder cycle is missing. Method 700 may judge that the first
voltage pulse of the ignition coil command sequence for a cylinder
cycle is missing when the first voltage pulse has not been detected
before a second voltage pulse (e.g., long duration pulse width) for
the ignition coil command sequence is detected. The first voltage
pulse is a begin charging command for a second ignition coil. The
second voltage pulse indicates charging and discharging time for
the first ignition coil. For example, if a short duration voltage
pulse is not detected by interpretive logic before a long duration
voltage pulse is detected, it may be determined that the first
voltage pulse for a cylinder cycle is absent or missing. In other
examples, it may be determined that the first voltage pulse is not
present if the engine rotates through a crankshaft angle without
detecting the first voltage pulse. If method 700 judges that the
first voltage pulse is missing, the answer is yes and method 700
proceeds to 706. Otherwise, the answer is no and method 700
proceeds to 708.
At 706, method 700 opens an ignore window after a falling edge of a
second voltage pulse (e.g., long duration pulse width) is detected.
By opening the ignore window, short duration (e.g., second ignition
coil commands) pulses are not acted upon to charge or discharge the
second ignition coil. Alternatively, the ignore window may be
opened at a predetermined crankshaft angle during the cylinder
cycle. FIG. 5 shows an example of the way method 700 opens the
ignore window and does not respond to short duration voltage pulses
that occur during the time the ignore window is open so that the
second ignition coil is not charged in a cylinder cycle when the
first voltage pulse is missing or not detected. For example, if the
first voltage pulse of a cylinder cycle is missing and the third
voltage pulse is present, the third voltage pulse does not cause
the second ignition coil to charge or discharge as is shown in FIG.
5. The ignore window is opened for a predetermined amount of time
or crankshaft degree interval. Method 700 proceeds to exit after
the ignore window is opened and closed as described in FIG. 5.
At 708, method 700 judges if a second voltage pulse (e.g., long
duration pulse width) of an ignition coil command sequence for a
cylinder cycle is missing. Method 700 may judge that the second
voltage pulse of the ignition coil command sequence for a cylinder
cycle is missing when a third voltage pulse of the ignition coil
command sequence has been detected without detecting the second
voltage pulse in the cylinder cycle. The first voltage pulse is a
begin charging command for a second ignition coil. The second
voltage pulse indicates charging and discharging time for the first
ignition coil. The third voltage pulse indicates the discharge time
for the second ignition coil. In other examples, it may be
determined that the second voltage pulse is not present if the
engine rotates through a crankshaft angle without detecting the
second voltage pulse. If method 700 judges that the second voltage
pulse is missing, the answer is yes and method 700 proceeds to 710.
Otherwise, the answer is no and method 700 proceeds to 712.
At 710, method 700 opens an ignore window after a falling edge of a
third voltage pulse (e.g., short duration pulse width) is detected
as shown in FIG. 6. By opening the ignore window, short duration
(e.g., second ignition coil commands) pulses are not acted upon to
charge or discharge the second ignition coil. Further, the charging
current of the second ignition coil is slowly reduced so as to not
induce spark at a spark plug that is in electrical communication
with the second ignition coil. Alternatively, the ignore window may
be opened at a predetermined crankshaft angle during the cylinder
cycle. FIG. 6 shows an example of the way method 700 opens the
ignore window and does not respond to short duration voltage pulses
that occur during the time the ignore window is open so that the
second ignition coil is not discharged in a cylinder cycle when the
second voltage pulse is missing or not detected. For example, if
the second voltage pulse of a cylinder cycle is missing and the
third voltage pulse is present, the second ignition coil is not
discharged when the third voltage pulse is detected as is shown in
FIG. 6. The ignore window is opened for a predetermined amount of
time or crankshaft degree interval. In one example the ignore
window is open for 10 milliseconds after a falling edge of a second
voltage pulse is detected in a next cylinder cycle as is shown in
FIG. 6. Method 700 proceeds to exit after the ignore window is
opened and closed as described in FIG. 6.
At 712, method 700 judges if a third voltage pulse (e.g., short
duration pulse width) of an ignition coil command sequence for a
cylinder cycle is missing. Method 700 may judge that the third
voltage pulse of the ignition coil command sequence for a cylinder
cycle is missing when the third voltage pulse has not been detected
a predetermined amount of time after the first or second voltage
pulse (e.g., short or long duration pulse width) during the
cylinder cycle is detected. The third voltage pulse is a discharge
command for a second ignition coil. For example, if a short
duration voltage pulse is not detected by interpretive logic after
a long duration voltage pulse is detected, it may be determined
that the third voltage pulse for a cylinder cycle is absent or
missing. In other examples, it may be determined that the third
voltage pulse is not present if the engine rotates through a
crankshaft angle without detecting the third voltage pulse. If
method 700 judges that the third voltage pulse is missing, the
answer is yes and method 700 proceeds to 714. Otherwise, the answer
is no and method 700 proceeds to 716.
At 714, method 700 opens an ignore window a predetermined amount of
time after a falling edge of the second voltage pulse (e.g., long
duration pulse width) is detected. By opening the ignore window,
short duration (e.g., second ignition coil commands) pulses are not
acted upon to charge or discharge the second ignition coil.
Alternatively, the ignore window may be opened at a predetermined
crankshaft angle during the cylinder cycle after the third voltage
pulse is not detected. FIG. 4 shows an example of the way method
700 opens the ignore window and does not respond to short duration
voltage pulses that occur during the time the ignore window is open
so that the second ignition coil is not charged in a cylinder cycle
when the first voltage pulse is missing or not detected. For
example, if the third voltage pulse of a cylinder cycle is missing
and the first and second voltage pulses are present, the third
voltage pulse does not cause the second ignition coil to discharge
as is shown in FIG. 4. The ignore window is opened for a
predetermined amount of time or crankshaft degree interval.
Further, charge in the second ignition coil is slowly reduced over
time by reducing charging current supplied to the second ignition
coil so that the second ignition coil does not induce a spark at a
spark plug that is electrically coupled to the second ignition coil
during the cylinder cycle as is shown in FIG. 4. Method 700
proceeds to exit after the ignore window is opened and closed as
described in FIG. 4.
At 716, method 700 charges and discharges first and second ignition
coils during a cylinder of a cylinder to provide spark to the
cylinder. In one example as shown in FIG. 3, method 700 charges a
second ignition coil in response to a first voltage pulse during a
cylinder cycle. Method 700 charges and discharges a first ignition
coil in response to a second voltage pulse during the cylinder
cycle. Method 700 discharges the second ignition coil in response
to a third pulse during the cylinder cycle. Thus, two commands to
two different ignition coils are provided via three voltage pulses.
The voltage pulses are distinguished from each other by the
duration of the voltage pulses. Longer duration voltage pulses are
commands for the first ignition coil. Shorter duration voltage
pulses are commands for the second ignition coil. Method 700
proceeds to exit after spark is provided during a cylinder cycle as
is shown in FIG. 3.
In this way, charging and discharging of the second ignition coil
during a cylinder cycle may be prevented in response to one or more
missing voltage pulses that comprise an ignition coil command
sequence. Further, the method provides for soft shutdown of the
second ignition coil if the second ignition coil has started to
charge and a missing second or third voltage pulse is
determined.
Thus, the method of FIG. 7 provides for a method for providing
spark to an engine, comprising: commanding two different ignition
coil charging current times via a single conductor and two ignition
coil commands; and ignoring a second portion of a first of the two
ignition coil commands in response to an absence of a first portion
of the first of the two ignition coil commands. The method includes
where two ignition coil commands are provided during a single cycle
of a cylinder. The method includes where the two ignition coil
commands are directed to a first ignition coil and a second
ignition coil, and further comprising not charging and discharging
the first ignition coil and the second ignition coil in a cylinder
cycle in response to the absence of the first portion of the first
of the two ignition coil commands in the cylinder cycle.
In some examples, the method includes where the two ignition coil
commands include a command to a first ignition coil comprising a
single voltage pulse. The method includes where the two ignition
coil commands include a command to a second ignition coil
comprising of two voltage pulses. The method includes where
ignoring the second portion of the first of two ignition coil
commands includes taking no action to charge or discharge an
ignition coil in response to presence of a voltage pulse.
The method of FIG. 7 also provides for a method for providing spark
to an engine, comprising: commanding two different ignition coil
charging current times via a single conductor and two ignition coil
commands for a cylinder cycle; and ignoring the presence of at
least one voltage pulse providing at least a portion of the two
ignition coil commands in response to a voltage pulse missing from
the two ignition coil commands. The method includes where the two
ignition coil commands are comprised of at least three separate
voltage pulses of two pulse widths.
In some examples, the method includes where ignoring the presence
of the at least one voltage pulse includes not charging or
discharging an ignition coil in response to a presence voltage
pulse. The method includes where a second ignition coil is not
charged in the cylinder cycle in response to an absence of a first
portion of a first command of the two ignition coil commands. The
method includes where a second ignition coil is not discharged to
provide a spark at a spark plug in the cylinder cycle in response
to an absence of a second command of the two ignition coil
commands. The method includes where a second ignition coil is not
discharged to provide a spark at a spark plug in the cylinder cycle
in response to an absence of a second portion of a first command of
the two ignition coil commands. The method includes where the two
ignition coil commands are a basis for providing spark at a single
spark plug. The method further comprises charging and discharging a
first ignition coil in response to a voltage pulse of a second
command of the two ignition coil commands.
In still other examples, the method provides for providing spark to
an engine, comprising: commanding two different ignition coil
charging current times via a single conductor and two ignition coil
commands, a first of the two ignition coil commands adjusting
charging of a second ignition coil, a second of the two ignition
coil commands adjusting charging of a first ignition coil;
adjusting charging of the second ignition coil responsive to an
absence of a first portion of the first of the two ignition coil
commands in a first manner; adjusting charging of the second
ignition coil responsive to an absence of a second portion of the
first of the two ignition coil commands in a second manner; and
adjusting charging of a first ignition coil responsive to an
absence of a second of the two ignition coil commands in a third
manner.
The method includes where two ignition coil commands are provided
during a single cycle of a cylinder, and where the first manner
includes not charging the second ignition coil in a cylinder cycle
where the first portion of the first of the two ignition coil
commands is absent. The method includes where the two ignition coil
commands are directed to the first ignition coil and the second
ignition coil, and where the second manner includes continuing to
charge the second ignition coil in a cylinder cycle where the
second portion of the first of the two ignition coil commands is
absent. The method includes where the two ignition coil commands
include a command to a first ignition coil comprising a single
voltage pulse, and where the third manner includes charging and
discharging the second ignition coil without providing a spark at a
spark plug in a cylinder cycle where the second of the two ignition
coil commands is absent. The method includes where the two ignition
coil commands include a command to a second ignition coil
comprising two voltage pulses. The method includes where a spark is
not induced at a spark plug coupled to the second ignition coil
when adjusting charging of the second ignition coil in the first
and second manners.
As will be appreciated by one of ordinary skill in the art,
routines described in FIG. 7 may represent one or more of any
number of processing strategies such as event-driven,
interrupt-driven, multi-tasking, multi-threading, and the like. As
such, various steps or functions illustrated may be performed in
the sequence illustrated, in parallel, or in some cases omitted.
Likewise, the order of processing is not necessarily required to
achieve the objects, features, and advantages described herein, but
it is provided for ease of illustration and description. The
methods and sequences described herein may be provided via
executable instructions stored in non-transitory memory of a
control in the system or systems described herein. Although not
explicitly illustrated, one of ordinary skill in the art will
recognize that one or more of the illustrated steps or functions
may be repeatedly performed depending on the particular strategy
being used.
This concludes the description. The reading of it by those skilled
in the art would bring to mind many alterations and modifications
without departing from the spirit and the scope of the description.
For example, I3, I4, I5, V6, V8, V10, and V12 engines operating in
natural gas, gasoline, or alternative fuel configurations could use
the present description to advantage.
* * * * *